1. Field of the Invention
The present invention generally relates to semiconductor devices and methods of producing the same, and more particularly to a semiconductor device having a chip size package (CSP) structure and a method of producing the same.
Recently, attempts have been made to produce a smaller size semiconductor device having a higher density in order to meet a demand for a smaller electronic device and apparatus. Proposed as such a smaller size semiconductor device is a semiconductor device having a so-called CSP structure, which is downsized by being shaped as close to a semiconductor element (chip) as possible.
A downsized high-density semiconductor device with an increased number of pins requires pitches between its external connection terminals to be narrowed. Therefore, a protrusion electrode (bump) is employed as an external connection terminal so that a relatively large number of external connection electrodes can be formed in a reduced space.
2. Description of the Related Art
FIGS. 1 and 2 show a conventional semiconductor device 10. FIG. 1 is a sectional view of the semiconductor device 10 and FIG. 2 is a plan view of the semiconductor device 10 without a sealing resin 14. The semiconductor device 10 is downsized by being formed to have the CSP structure. The semiconductor device 10 includes a semiconductor substrate 11 in a chip state, interconnection lines 18, protrusion electrodes for signal (hereinafter, protrusion signal electrodes) 12, protrusion electrodes for ground (hereinafter, protrusion ground electrodes) 13 and the sealing resin 14.
The upper surface of the semiconductor substrate 11 in FIG. 1 is a circuit-containing surface on which a circuit including pads for signal (hereinafter, signal pads) 15 and pads for ground (hereinafter, ground pads) 16 is formed. An insulating film is formed on the circuit-containing surface except for the positions where the signal and ground pads 15 and 16 are formed. The insulating film provides protection for the circuit-containing surface.
The interconnection lines 18 are formed directly on the upper surface of the insulating film 17 in a predetermined pattern. One end portion of each of the interconnection lines 18 is connected to one of the signal pads 15 or the ground pads 16, while one of the protrusion signal electrodes 12 or the protrusion ground electrodes 13 is formed on the other end portion of each of the interconnection lines 18. The protrusion signal and ground electrodes 12 and 13 serve as the external connection terminals of the semiconductor device 10.
Further, the sealing resin 14 is formed to cover the circuit-containing surface of the semiconductor substrate 11 so as to protect the insulating film 17, the interconnection lines 18, and the protrusion signal and ground electrodes 12 and 13. However, the upper end surfaces of the protrusion signal and ground electrodes 12 and 13 are uncovered and appear from the sealing resin 14.
As described above, the semiconductor device 10 having the conventional CSP structure has the interconnection lines 18 formed on the insulating film 17 so as to electrically connect the signal and ground pads 15 and 16 and the corresponding protrusion signal and ground electrodes 12 and 13. The interconnection lines 18 serve as interposers, thus allowing the signal and ground pads 15 and 16 to be formed at a distance from the protrusion signal and ground electrodes 12 and 13. This gives more latitude in determining where to dispose the protruding signal and ground electrodes 12 and 13, and also allows the semiconductor device 10 to accommodate an increased number of pins.
However, according to the conventional semiconductor device 10, the interconnection lines 18 serving as the interposers each have a single-layer structure, thus restricting the layout of the interconnection lines 18. Therefore, a layout of the interconnection lines 18 considering an electrical characteristic is prevented from being formed. In other words, the semiconductor device 10 having the conventional CSP structure is downsized to have only a limited region for forming the interconnection lines 18. Forming a large number of the interconnection lines 18 in the region would require each of the interconnection lines 18 to have a narrower line width, thus causing the impedance of each of the interconnection lines 18 to become higher.
On the other hand, a high-frequency clock has been employed in the semiconductor substrate 11 to meet a demand for a higher processing speed. Therefore, a signal input to or output from each of the signal pads 15 via a corresponding one of the interconnection lines 18 becomes a high-frequency signal, which may generate interference between adjacent two of the interconnection lines 18. Thus, the restriction on the layout of the interconnection lines 18 prevents the semiconductor device 10 having the conventional CSP structure from realizing the higher processing speed.
It is a general object of the present invention to provide a semiconductor device in which the above disadvantages are eliminated and a method of producing the same.
A more specific object of the present invention is to provide a semiconductor device having an improved electrical characteristic and a method of producing the same.
The above objects of the present invention are achieved by a semiconductor device including a semiconductor substrate including a plurality of signal pads and ground pads, an insulating film formed on the semiconductor substrate, a conductive metal film formed on the insulating film and electrically connected to the ground pads and a plurality of first interconnection lines electrically connected to the signal pads and insulated from the conductive metal film, wherein the conductive metal film is formed over a region including the first interconnection lines in a plan view of the semiconductor device.
According to the above-described semiconductor device, since the conductive metal film is formed to be electrically connected to the ground pads, the conductive metal film can be employed as a ground layer having a ground potential. Further, the conductive metal film is formed over the region including the interconnection lines in the plan view of the semiconductor device. Therefore, the conductive metal film can be formed over a wide area without being restricted by the positions of the interconnection lines.
As is known, an electrical resistance is inversely proportional to the cross-sectional area of a conductive material. Therefore, the wide formation area of the conductive metal film, that is, the wide cross-sectional area of a ground, lowers a ground impedance. As a result, the semiconductor device is provided with an improved electrical characteristic so as to become a fast semiconductor device employing a high frequency. Since the conductive metal film is electrically insulated from the interconnection lines, the conductive metal film does not cause a short circuit between the interconnection lines and the ground.
The above objects of the present invention are also achieved by a semiconductor device including a semiconductor substrate including a plurality of signal pads and ground pads, an insulating film formed on the semiconductor substrate, a conductive metal film electrically connected to the ground pads, a plurality of first interconnection lines electrically connected to the signal pads and insulated from the conductive metal film and a plurality of metal films electrically connected to the first interconnection lines and insulated from the conductive metal film, wherein the conductive metal film is formed over a region including the first interconnection lines in a plan view of the semiconductor device.
The above objects of the present invention are also achieved by a semiconductor device including a semiconductor substrate including a plurality of signal pads and ground pads, an insulating film formed on the semiconductor substrate, a first conductive metal film formed on the insulating film and electrically connected to the ground pads, a second conductive metal film electrically connected to and formed on the first conductive metal film, and a plurality of interconnection lines electrically connected to the signal pads and insulated from the first and second conductive metal films, wherein the first and second conductive metal films are formed over a region including the interconnection lines in a plan view of the semiconductor device.
The above objects of the present invention are further achieved by a method of producing a semiconductor device comprising the steps of (a) forming a first insulating film on a semiconductor substrate including signal and ground pads except for positions where the signal and ground pads are formed, (b) forming a conductive metal film on the first insulating film except for the positions where the signal pads are formed, (c) forming a second insulating film over the conductive metal film, (d) forming interconnection lines on the second insulating film, (e) forming protrusion electrodes each having a predetermined height on the interconnection lines and (f) providing resin sealing on the first and second insulating films, the conductive metal film, the interconnection lines and sides of the protrusion electrodes.